Many procedures have been used for extracting stones and stone fragments such as ureteral stones, calaceal stones and other calculus and the like from various biological systems such as renal and biliary systems. For example, ureteroscopy is the passage of a narrow caliber urinary endoscope within the ureteral lumen and is most commonly performed for the treatment and removal of painful ureteral stones that will not pass spontaneously. Ureteroscopy allows stone visualization and provides access for the delivery, guidance, and actuation of stone removal and/or fragmentation devices.
Typically, stone removal is accomplished with a retrieval basket. Existing stone retrieval baskets are constructed with inner and outer components. The inner component is typically a multi-filament wire generally composed of three to four strands that naturally separate and expand to form an oval shaped basket near the end and then rejoin at their terminus to a tapered tip. The outer component is a narrow cylindrical tube generally composed of plastic that encases the inner wire core and basket. When the wire inner component is pulled through the outer member, the flexible wires collapse so as to completely withdraw into the outer casing and collapse the basket. Typically a stone retrieval basket is passed beyond the stone either without or after fragmentation. The inner core is then advanced within and past the end of the outer sheath by manipulation of a handle on the proximal (surgeon's) end of the device. The inner core filaments then expand to form the basket and the surgeon manipulates the stone into the basket. Once the stone is entrapped in the basket, the inner core is withdrawn partially into the outer sheath so as to narrow the basket and securely capture the stone. Since the inner core cannot be completely withdrawn due to entrapped stone, the outer diameter of the basket is now larger than the fully collapsed device. The degree to which the basket is narrowed is visually controlled by the surgeon so as to insure the stone is firmly trapped.
Small stones may be simply grasped with a basket passed through the working channel of the ureteroscope. However, larger stones require fragmentation into smaller particles before they can be safely removed without injury to the ureter. In some cases, the stone may be completely fragmented into pieces so small that they will naturally pass out of the patient on their own without extraction. Occasionally, stones felt to be suitable for simple extraction will become immovable within narrowed segments of the ureteral lumen after basket entrapment. It is then difficult to disengage the stone from the basket for initial or additional fragmentation, and fragmentation within the basket is complicated.
Stone fragmentation is generally carried out via ultrasonic, ballistic, or laser methods. A fragmentation device is passed through the working channel of the ureteroscope and fragmentation is then performed. Stones are not held firmly in place during fragmentation making completion of fragmentation difficult to judge, and allowing some pieces that are still too large to pass naturally, to migrate proximally up the ureter where they may be difficult to re-engage or retrieve. Generally, once fragmentation is complete, the fragmentation device is removed and the basket is passed to entrap the remaining pieces. As such, two separate devices are necessary to complete fragmentation and removal.
Fragmentation without entrapment permits stone migration and loss. Fragmentation would be far more effective if the stone were held firmly in place so it could not recoil away from the fragmenting tip. Stone entrapment either without or after some fragmentation can be problematic in that even small stones, or those initially deemed to be adequately broken up, may be difficult to withdraw through the tight portion of the ureter.
Generally, stones are broken up until the fragments appear to be small enough to ensnare safely. Complete fragmentation may be hindered, however, by vision, ureteral edema, and fear of proximal migration. Even when the stones are adequately broken, stone fragments may be left behind because conventional baskets are not optimized for removal of shattered stones. Stone fragments left in the body may not be excreted as quickly or as completely as desired. Accordingly, there is a need in the art for an improved surgical instrument for fragmenting and/or extracting stones and the like.